Sorry, you're absolutely right, I should have definitely included Lincoln Chafee, Jim Webb, Martin O'Malley, and Larry Lessig on the Dem side of things. But you have to admit, the surprise over Donald Trump having locked up the GOP nomination at this point, that is matched only by the surprise over Hillary Clinton having not locked up the Dem nomination by now. I believe the reason for this is that the anti-establishment sentiment is running very strong within both major parties, but I could be completely off base.
It's the difference between delegate apportionment rules rather than the strength or weakness of a candidate. If the Dems had identical delegate rules to the GOP, Clinton would've actually -reached- the minimum delegate total for the nomination a month or so ago and we'd be talking about Trump having not clinched it despite no opponents after a certain point.